Patent EA-002464-B1 (EA)
Title: Novel fluids and techiques for maximizing fracture fluid clean-up
Inventor: HINKEL JERALD J
IPC: C09K8/52
Filed: 1999-09-23
Abstract: 1. A method for fracturing a subterranean formation comprising sequentially injecting into a wellbore, fracturing fluid thereby creating a fracture, said fluid comprising a suite of breakers or a single breaker at varying concentrations, to induce a mobility gradient, such that fracturing fluid near a fracture tip has a higher differential mobility than fracturing fluid near the wellbore. 2. A method for fracturing a subterranean formation comprising the steps of: injecting fluid into a wellbore at a pressure greater than the minimum in situ rock stress, thereby creating a fracture; co-injecting with said fluid, at least one breaker to induce a mobility differential within said fracture along the direction of said fracture; allowing said fluid to migrate towards said wellbore in response to said mobility differential. 3. The method of claim 2 wherein said mobility differential is a viscosity gradient. 4. The method of claim 2 wherein said mobility differential is a density gradient. 5. The method of claim 2 wherein said mobility differential is both a viscosity gradient and a density gradient. 6. A method for fracturing a subterranean formation comprising injecting a heterogeneous sequence of breakers into a wellbore at pressures greater than the minimum in situ rock stress, thereby creating a fracture, wherein said breakers induce a mobility differential. 7. The method of claim 6 wherein said heterogeneous fluid consists of at least a first stage and a second stage. 8. The method of claim 7 wherein said first stage is comprised of a proppant-carrying matrix, a high-activity breaker, and a gas. 9. The method of claim 7 wherein said second stage is comprised of a proppant-carrying matrix, a lower-activity breaker, and a means for controlling proppant flowback. 10. The method of claim 7 wherein said first stage is comprised of a proppant-carrying matrix, and an encapsulated bromate breaker. 11. The method of claim 10 wherein said first stage further comprises a member selected from the group consisting of nitrogen, air, and carbon dioxide. 12. The method of claim 11 wherein said encapsulated bromate breaker is present in said fluid at a concentration of about 240g per 1000 liters of fluid. 13. The method of claim 12 wherein said second stage is in turn comprised of a proppant-carrying matrix, and an encapsulated bromate breaker. 14. The method of claim 13 wherein said encapsulated bromate breaker is present in said fluid at a concentration of about 120g per 1000 liters of fluid. 15. The method of claim 14 further comprising a third stage. 16. The method of claim 15 further comprising a fourth stage. 17. The method of claim 16 further comprising a fifth stage. 18. The method of claim 17 further comprising a sixth stage. 19. The method of claim 18 further comprising a seventh stage. 20. The method of claim 19 further comprising an eighth stage. 21. The method of claim 20 further comprising a ninth stage. 22. The method of claim 21 wherein said third through ninth stage contain the same or different breakers, and if the same, then each stage has a lower breaker activity than the previous stage. 23. The method of claim 14 further comprising a final stage. 24. The method of claim 23 wherein said final stage is in turn comprised of a proppant-carrying matrix, a breaker, and a means for controlling proppant flowback. 25. The method of Claim 24 wherein said means for controlling proppant flowback is selected from the group consisting of NOVALOID fibers, NOVALOID platelets, NOVALOID fibers and platelets, NYLON fibers, and glass fibers. 26. The method of Claim 25 wherein said means for controlling proppant flowback is PropNET GOLD. 27. The method of claim 6 further comprising the step of: within one hour after creating said fracture, opening said wellbore and allowing said fluid to flow back thereby rapidly lowering pressure in said fracture. 28. The method as in any of claims 1-6 wherein said fluid is comprised of at least a first, a second, and a third stage, and wherein said at least three stages are sequentially injected into said wellbore beginning with said first stage, and wherein: said first stage is comprised of a proppant-carrying matrix, a first breaker, and a member selected from the group consisting of gas, foam, and energized fluid; said second stage is comprised of a means for controlling proppant flowback, a proppant-carrying matrix, and a second breaker; and wherein said first breaker is the same or different than said second breaker, and if the same, then the concentration of said first breaker is greater than the concentration of said second breaker. 29. The method of claim 28 further comprising the step of within one hour after creating said fracture, opening said wellbore and allowing said fluid to flow back thereby rapidly lowering pressure in said fracture. 30. A method for fracturing a subterranean formation comprising injecting through a wellhead into a wellbore, a foamed fracturing fluid thereby creating a fracture, said fluid in at least one early stage containing proppant, injecting into said wellbore, means for controlling proppant flowback in at least one later stage, opening said wellhead soon after completion of pumping to allow flowback and thereby forcing closure of said fracture. 31. A method for fracturing a subterranean formation according to a pumping schedule to achieve differential mobility, comprising: injecting a fracturing fluid containing proppant into said formation, thereby creating a fracture, wherein said fluid has greater mobility than subsequent stages upon end of treatment; thereafter, injecting a means for controlling proppant flowback into said formation; thereafter, promoting aggressive flowback by forced closure. 32. The method of claim 31 wherein said fluid is combined with a gas prior to injecting, said gas selected form the group consisting of nitrogen, carbon dioxide, and air. 33. A process for designing a fracturing treatment comprising selecting a suite of breakers and breaker concentrations to achieve differential mobility. 34. A device comprising a pre-recorded computer-readable means, said means selected from the group consisting of a magnetic tape, a magnetic disk, an optical disk, a CD-ROM, and a DVD-ROM, wherein said device carries instructions for the process of Claims 1 to 33.